Is Test and Balance Necessary??

[BBeerme]

Which brings up another point. So far, for whatever reason, I've been thinking air flow for the most part.

When it comes to hydronics, then it can be much more critical. Sure, you might get lucky, but in my experience, balancing the flow through the various devices is very important for proper operation, long life, and overall efficiency.

[WAYNE3298]

Chilled water balance is the most critical. Hot water is so forgiving it's hard to screw up unless the system is under designed. Chilled water balance forces water where you want it by limiting the amount of water any device can take. If not balanced properly chilled water systems can be a disaster. Believe it or not most balancers are not good at water balance.

[BBeerme]

I've done a few through the years. Depending on the age of the system, the location of the circuit setters, and if the original engineering prints are available, sometimes it goes fast, but it usually takes more time than you think it will. At least if you keep going back to check and recheck everything after you've already made one or two passes.

Chilled water balance is the most critical. Hot water is so forgiving it's hard to screw up unless the system is under designed. Chilled water balance forces water where you want it by limiting the amount of water any device can take. If not balanced properly chilled water systems can be a disaster. Believe it or not most balancers are not good at water balance.

[WAYNE3298]

After you have done a lot of water balance it gets a lot easier. The recommended method is to preset the circuit setters by calculating the pressure drop needed. In my opinion that is a waste of time. If you start nearest the pump and set the flow slightly lower than design two passes will usually do it. When I was doing a lot of water balance I fairly often got almost all of them on the first pass. Even at that you still have to read the circuit setters twice.

[Scoobie]

Wayne, we always use auto-flow valves on vavs. They still need to be checked during tab, but no adjustment needed.

[Cagey57]

Wayne,
To respond to the title of the thread, ABSOLUTELY in the context of Hydronics and VAV Systems !
After being a "Controls Guy" for 23+ years a good TAB person is worth every cent.

Readers Digest version of 1 particular project: 7 Story building retrofit of 2 RTU's and 150+ VAV boxes. Told the customer "you really need to re-balance". They drug their feet for 6 month, finally consented and we recommended 3 TAB companies (all 3 excellent). 6 months after TAB completed Chief Building Engineer tells me that the "Energy savings paid for the Balance 2 month ago" !

I agree with retro-commissioning, to a point. Too many of the folks that do it try to justify their existence with a mountain of paperwork and less than complete TAB.

[heatingman]

Wayne, we always use auto-flow valves on vavs. They still need to be checked during tab, but no adjustment needed.

With those, the more important part of the balancing is the riser balance in a high rise, or the main branch lines in a more sprawling system.

The smaller terminals are less important, but the key to any balance is a completed system, clean strainers, correct rotation, and every valve open and a properly filled system .

But most times balancing is “done” in steps before the system is totally complete.




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[BBeerme]

Yeah, I'm sure if I did a lot more of it, I would've gotten faster/better. But since I only did a few, and probably a year or more apart, well, you get the idea.

After you have done a lot of water balance it gets a lot easier. The recommended method is to preset the circuit setters by calculating the pressure drop needed. In my opinion that is a waste of time. If you start nearest the pump and set the flow slightly lower than design two passes will usually do it. When I was doing a lot of water balance I fairly often got almost all of them on the first pass. Even at that you still have to read the circuit setters twice.

[WAYNE3298]

Scoobie,
The auto flow valves do control maximum flow. Reading the pressure drop across them only tells you if you have enough differential across the valve for it to work but doesn't tell the flow. When I was balancing full time the complaint with them was they started having problems after about 2 years. I don't know if that's still true.

[Scoobie]

Scoobie,
The auto flow valves do control maximum flow. Reading the pressure drop across them only tells you if you have enough differential across the valve for it to work but doesn't tell the flow. When I was balancing full time the complaint with them was they started having problems after about 2 years. I don't know if that's still true.

It’s the norm around here on big or small jobs. Tab guys ain’t real happy if you use circuit setters. Pressure independent control valves is the new hot thing. I personally don’t see what’s so great about the picv s.

[WAYNE3298]

Heatingman the reason some engineers hated me is I did make them accountable. There were contractors that banned me from meetings because as they said "we are afraid of what you will say". I told them the truth and apparently it hurt. I had engineers trying to tell me how to test HVAC systems that had never done it even one time. One engineer who not only didn't know my job but didn't know his either said I was doing my own thing. I said you are damn right I am and it is my thing not yours. One thing I enjoyed was when the fire marshal came to witness testing of the smoke fans the engineer poised himself to supervise the test. The fire marshal ask who was the balancer and found out it was me. He turned to the engineer and said the balancer is going to run this test.

[WAYNE3298]

Why don't the TAB guys like circuit setters? Usually the ones I knew that didn't like them didn't like water balance because they didn't know how to do it. I don't like the circuit setters that read out in inches because it doesn't take much system instability to make them impossible to set.

[Scoobie]

They know how to balance them. They just take a lot longer.

[BBeerme]

LOL

Heatingman the reason some engineers hated me is I did make them accountable. There were contractors that banned me from meetings because as they said "we are afraid of what you will say". I told them the truth and apparently it hurt. I had engineers trying to tell me how to test HVAC systems that had never done it even one time. One engineer who not only didn't know my job but didn't know his either said I was doing my own thing. I said you are damn right I am and it is my thing not yours. One thing I enjoyed was when the fire marshal came to witness testing of the smoke fans the engineer poised himself to supervise the test. The fire marshal ask who was the balancer and found out it was me. He turned to the engineer and said the balancer is going to run this test.

[hvacker]

I think he only reason T&B is done at all is it's on the spec. or complaints are through the roof.
I remember reading a T&B report in a contractors office. I told them that the report was incorrect. He told me he didn't care. All he cared about was the NEBB stamp. Getting paid was most important.